Adjustable support posts or columns are well known in the art. Typically, conventional support columns, such as lifting jacks for lifting and supporting of various structures employ a single, threaded support rod disposed in a main column. Many of these assemblies comprise a main column composed of two or more telescoping elements which can be extended and locked at predetermined intervals, such that the column can be adjusted to a length which is slightly shorter than that which is actually required. The threaded support rod, which may either engage an internal screw in the main column or an adjusting nut which bears on the top of the column, is then extended as required to support and/or raise the structure in question.
In many situations, the main column will be extended and locked into a position, and thereafter will not be further adjusted. The adjusting screw therefore constitutes the primary height adjusting means, while the main column remains locked at one length. Typically, however, adjustable columns are made as an integrated unit. Thus one is forced to purchase a large (and in some cases complex) adjustable column, even if the adjustment capabilities of the main column are not to be used. This unnecessarily increases the cost incurred by the user in order to obtain an adjustable column.
Furthermore, because the main column typically includes substantially rigid telescoping elements, it is not possible to employ the column within a space which is shorter than the shortest length (or substantially longer than the maximum extended length) of the main column. This means that one is forced to first measure the height of the location in which the column is to be placed, obtain a column having an appropriate length, and then install the column. This is a time consuming and laborious process, and, because the column almost invariably has a greater range of adjustment than is actually required, unnecessarily expensive. Furthermore, it is necessary for suppliers to stock adjustable columns having various sizes and extension capabilities, which results in increased storage costs, which are invariably passed on to the user.
U.S. Pat. No. 3,027,140 discloses an adjustable element which is adapted to be quickly and removably fitted to a fixed length column. The disclosed adjustable element comprises an adjusting screw and nut, a bearing plate, and a base plate. The adjustable element is intended to be used in conjunction with a column or post which is obtained separately, and cut approximately to length, by the user, on site.
This overcomes many of the above-stated problems related to adjustable columns. However, in a case where the column is made of wood, a hole must be bored into the end of the post in order to receive the adjusting screw. This hole must be carefully aligned with the central axis of the post, and must be properly sized so that the screw can slide within the hole, while being substantially prevented from rotation due to off-centre loading. Thus satisfactory on-site fabrication of the adjustable column is dependent on the skill of the builder, and may require special tools, thereby adding to the cost of installation of the post.
When the column is made using a metal pipe, it is necessary to employ spacer elements between the adjusting screw and the interior of the pipe. These adjusting members are intended to substantially prevent rotation of the adjusting screw due to off-centre loading. However, the requirement for purchasing spacer elements increases the cost of the column, and places a restriction on the size of the pipes which can be satisfactorily used.